Pre-authorization of bearer set-up

ABSTRACT

A request is received to install control rules before having received a corresponding QoS Authorization, especially where the QoS Authorization requires a prior reservation of resources. The request for a bearer resource is pre-authorized before having received a QoS authorization for said request, by receiving a request for a bearer resource; determining that a QoS authorization has, not been received yet; pre-authorizing said request for the bearer resource by installing initial control rules; and updating the previously installed initial control rules with final control rules upon receipt of the QoS authorization. This pre-authorization and the submission of initial control rules are carried out from a PCRF server towards a PCEF device, before having received the QoS authorization. In particular, the pre-authorization may be triggered from a P-CSCF at the originating or destination side, or at both.

TECHNICAL FIELD

The present invention generally relates to the acceptance of bearerrequests from the media plane whilst negotiation of bearer is pending atthe signalling plane. In particular, the invention relates to mechanismsfor pre-authorizing a bearer request at a Policing and Charging RulesFunction whilst the bearer is negotiated through entities of an IPMultimedia Subsystem.

BACKGROUND

An IP Multimedia Subsystem (hereinafter IMS) enables an operator of aPublic Land Mobile Network (hereinafter PLMN) to offer their subscribersmultimedia services based on and built upon Internet applications,services and protocols. These multimedia services may be particularlyaccessible via IMS applications.

A complete solution for the support of IMS applications, in accordancewith 3GPP IMS-related technical specifications, includes terminals forthe subscribers or users of the IMS, one or more IP-Connectivity AccessNetwork (hereinafter IP-CAN), and specific functional elements of theIMS as described in 3GPP TS 23.228: “IP Multimedia Subsystem; Stage 2”.An exemplary IP-CAN may be a GPRS core network with a GERAN and/or UTRANradio access networks. Ongoing 3GPP Release 8 also covers a so-calledSAE network as a new type of IP-CAN, in accordance with 3GPP TS 23.401.

Different services and applications can be offered on top of IMS. TheIMS allows deployment of peer-to-peer applications such as MultimediaTelephony, Push-to-Talk over Cellular, real-time video sharing, etc, forwhich the transport connections are dynamically negotiated by a protocolexchange between two end-points. Such protocol exchange isconventionally carried out by coupled protocols such as the SessionInitiation Protocol (hereinafter SIP) and the Session DescriptionProtocol (hereinafter SDP) may be, namely a SIP/SDP exchange.

In order to provide a satisfactory and reliable service experience,operators need to take special care of the quality, effective chargingand potential fraud on the use of services and IMS applications. To thisend, a Policy and Charging Control (hereinafter PCC) architecture isprovided, as disclosed in 3GPP TS 23.203, to help operators on thecontrol of the above issues. Thus, the PCC architecture cooperates withthe IMS in order to provide a selective control of IP flows, such asQoS, firewall, multiplexing, etc, as well as a selective handling of thenegotiated IP flows.

This PCC architecture generally includes an Application Function(hereinafter AF) offering applications that require policy and chargingcontrol of resources in the bearer plane and wherein servicecharacteristics are negotiated through in the signalling plane; a Policyand Charging Enforcement Function (hereinafter PCEF) providing servicedata flow detection, charging and policing enforcement over the trafficin the bearer plane and wherein the service is actually providedthrough; and a Policy and Charging Rules Function (hereinafter PCRF)providing control functions and installing rules at the PCEF to ensurethat only authorized media flows are allowed and are applied the rightQoS through the right bearer.

At present, the establishment of bearers can be initiated and managed bythe network (hereinafter NW) or by the user equipment (hereinafter UE)via so-called NW-initiated or UE-initiated Bearer Control Procedures. Inthis respect, the present invention is originally aimed for UE-initiatedBearer Control Procedures, though its teaching may solve similar issuesturning up in NW-initiated Bearer Control Procedures.

A conventional scenario may be where a user with a UE accesses the IMSthrough a Proxy Call Session Control Function (hereinafter P-CSCF) andgets IP connectivity via an IP-CAN such as GPRS. Where this scenarioincludes a PCC architecture, the AF is included in, or in closecooperation with, the P-CSCF; the PCEF may be included in, or in closecooperation with, a Gateway GPRS Support Node (hereinafter GGSN), aPacket Data Network Gateway (hereinafter PDN-GW), or any other networknode depending on the selected IP-CAN; and the PCRF may be provided as aseparate server logically located between the signalling plane and thebearer plane, or be integrated with the P-CSCF or the GGSN, or with anyother network node.

In a traditional scenario, where the PCC architecture is used, asequence for establishing an IMS session starts when the UE of anoriginating user submits a SIP Invite message including an SDP offertowards an originating P-CSCF acting as the entry to the IMS. This SDPoffer is transmitted through IMS Core nodes, that is, those IMS entitiesof the originating and/or destination IMS network that, for the purposeof the present invention, are not essential for the understanding of theproposed solution. Upon receipt of a corresponding SDP answer to theoriginating offer after having negotiated the media, the P-CSCF, orrather the AF included therein, submits a corresponding QoSauthorization towards the PCRF, whilst the P-CSCF forwards the receivedSDP answer towards the UE of the originating user, that is, theoriginating UE for the sake of simplicity. Afterwards, in a UE-initBearer Control mode, the originating UE initiates the reservation of QoSresources, namely a so-called bearer request throughout the presentspecification, towards the PCC architecture, namely towards the PCEFwhich asks the PCRF for applicable control rules. In the currentsituation, the QoS authorization always reaches the PCRF before havingbeen asked for applicable control rules for the bearer.

However, the 3GPP TS 23.228 states for Multimedia Telephony that, ifprovided with the appropriate rules, the reservation of bearer resourcesmay be initiated by the UE during the initial SIP Invite request. Inthis situation, the PCRF receives a request to install control rulesbefore having received any QoS Authorization from the P-CSCF, so thatsuch request is rejected in a conventional PCC architecture.

SUMMARY

It is an object of the present invention to obviate at least some of theabove disadvantages and provide for an enhanced PCC architecture whereinan, at least, temporary solution is offered to avoid rejection of arequest to install control rules received before having received acorresponding QoS Authorization. In this respect, a simple solution maybe the reattempt from the UE; however, such solution would not work in ascenario where the QoS Authorization is conditioned to a priorreservation of resources.

Thereby, the aim of the present invention is an enhanced PCCarchitecture wherein not only the problem of receiving a request toinstall control rules before having received a corresponding QoSAuthorization is solved, but also that such enhanced PCC architecturesolves the problem in scenarios where the QoS Authorization isconditioned to a prior reservation of resources.

The objects above are generally accomplished in accordance with theinvention by providing a method of authorizing a request for a bearerresource received before having received a QoS authorization for saidrequest, and enhanced entities of the PCC architecture cooperating tocarry out such method.

Thus, in accordance with a first aspect of the present invention, thereis provided a method of authorizing a request for a bearer resourcereceived before having received a QoS authorization for said request,the method comprising the steps of: receiving a request for a bearerresource; determining that a QoS authorization has not been received yetfor said request at a PCRF server; pre-authorizing said request for thebearer resource received before having received the QoS authorization;installing initial control rules applicable to the pre-authorizedrequest towards a PCEF device; and updating the previously installedinitial control rules with final control rules upon receipt of the QoSauthorization.

This pre-authorization along with the submission of initial controlrules towards the PCEF, before having received the QoS authorization,being a common inventive concept throughout the present specification.In particular, these initial control rules may include informationelements selected from: a rule identifier; a gate status; an incompleteservice data flow template, as obtainable from information provided bythe user equipment; QoS information including a QoS class identifier“QCI”, a guaranteed bit rate “GBR” and a maximum bit rate “MBR”, asrequested by the IP-CAN; and optional configured data such as charginginformation, service identifier, precedence, etc.

In this method, the initial control rules are temporary control rulesvalid only during a configurable time period without having received theQoS authorization at the PCRF server. That is, the pre-authorization inthis method is valid only during a configurable time period, so that themethod may further comprise a step of de-authorizing the bearer resourceupon expiry of said time period without having received the QoSauthorization. Moreover, the method may further comprise to this end astep of de-installing towards the PCEF device the initial control rulesafter expiry of said time period without having received the QoSauthorization.

In an embodiment of the invention, the step in this method of installingthe initial control rules towards the PCEF device may include a step ofindicating that are temporary control rules valid only during aconfigurable time period. In this embodiment, the method may furthercomprise a step of receiving at the PCRF server an indication from thePCEF device informing that the initial control rules have beende-installed after expiry of said time period, and a step of removingsaid initial control rules.

For the purpose of controlling the configurable time period, this methodmay further include a step of timing said configurable time periodduring which the pre-authorization and the initial control rules arevalid, and after which, without having received the QoS authorization,the corresponding bearer resource is de-authorized and the initialcontrol rules are de-installed. In particular, the step in this methodof timing the configurable time period may be carried out by at leastone of the PCRF server and the PCEF device.

Regarding the final control rules of this method, these final controlrules may include new control rules complementing the initial controlrules, in which case the method may further include a step of indicatingsuch complement from the PCRF server towards the PCEF device. If this isthe case, the method may advantageously further comprise a step ofadding said new control rules to the initial control rules previouslyinstalled at the PCEF device to configure the final control rules,without needing the removal and re-installation of unchanged initialcontrol rules.

Alternatively, where the final control rules are new control rules, themethod may further comprise a step of implicitly de-installing theinitial control rules and a step of installing the final control rulestowards the PCEF device.

In particular, the step in this method of installing initial controlrules may include a step of indicating installation with a “gate status”set to disabled, so that the bearer resources are reserved but trafficis still prevented on such bearer resources.

As an additional advantage, this method may further include a step ofobtaining a pre-authorization indication at the PCRF server from aP-CSCF server, which in particular may be the one in charge of providingthe QoS authorization.

In accordance with a second aspect of the present invention, there isprovided an enhanced PCRF server that comprises: a receiver forreceiving a QoS authorization of a bearer resource and for furtherreceiving a corresponding request for the bearer resource; a controlunit for determining a set of control rules to be installed for handlingthe requested bearer resource once authorized; and a sender forinstalling said set of control rules towards a PCEF device. In this PCRFserver, the control unit is arranged for pre-authorizing a request of abearer resource, the request received before having received the QoSauthorization; and the sender is arranged for installing initial controlrules applicable to the pre-authorized request and for further updatingthe previously installed initial control rules with final control rulesupon receipt of the QoS authorization.

As already commented above, the initial control rules in this PCRFserver are temporary control rules valid only during a configurable timeperiod without having received the QoS authorization.

In this respect, different alternatives may co-exist, likely dependingon configuration options that may be established per PCEF device basis.In one embodiment, the time period during which the initial controlrules are valid may be controlled in the PCRF server. To this end, thesender of the PCRF server may be arranged for de-installing towards thePCEF device the initial control rules after expiry of said time period.Not only the initial control rules, but also the pre-authorization inthis PCRF server is valid only during a configurable time period uponwhich expiry, without having received the QoS authorization, thecorresponding bearer resource may be de-authorized at the control unitof the PCRF server.

In another embodiment of the invention, the time period during which theinitial control rules are valid may be controlled in the PCEF device. Tothis end, the sender of the PCRF server may be arranged for installingthe initial control rules towards the PCEF device along with anindication of being temporary control rules valid only during aconfigurable time period. Under this embodiment, the receiver of thePCRF server may further be arranged for receiving an indication from thePCEF device informing that the initial control rules have beende-installed after expiry of said time period, and the control unit ofthe PCRF server may also be arranged for removing said initial controlrules.

With regard to the final control rules, the PCRF server may be designedso that the final control rules include new control rules complementingthe initial control rules. To this end, the sender of the PCRF servermay be arranged for indicating such complement towards the PCEF device.

Alternatively, the final control rules in the PCRF server may beconsidered new control rules submitted to implicitly de-install theinitial control rules towards the PCEF device.

In particular, and aligned with a corresponding technical feature of theabove method, the initial control rules may be installed from the PCRFserver towards the PCEF device with a “gate status” set to disabled.

In an embodiment of the invention, the PCRF server may be configured tocarry out the pre-authorization on its own and triggered from itscontrol unit; whereas in another embodiment of the invention, thepre-authorization may be carried out by the control unit of the PCRFserver upon receipt in the receiver of a pre-authorization indicationfrom the P-CSCF server. Irrespective of the embodiment followed in thisrespect, the QoS authorization for reserving a bearer may be received atthe receiver of the PCRF server from the P-CSCF server.

In accordance with a third aspect of the present invention, there isprovided an enhanced PCEF device for enforcing control rules on a perbearer resource basis, having a sender for submitting a request for abearer resource, a receiver for receiving control rules to be installedfor the bearer resource, and a control unit for applying the controlrules to the bearer resource. In this PCEF device the receiver isarranged for receiving initial control rules applicable to said bearerresource, pre-authorized by the above PCRF server before having a QoSauthorization available, and for receiving final control rules from thePCRF server to update said initial control rules, once the QoSauthorization is available, and the control unit is arranged forupdating said initial control rules with the final control rules uponreceipt of such updating from the PCRF server.

As described above, the initial control rules in this PCEF device aretemporary control rules valid only during a configurable time periodwithout having received the final control rules from the PCRF server.

In this respect, and in accordance with an embodiment of the invention,the receiver of the PCEF device may further be arranged for receiving ade-installation of said initial control rules from the PCRF server andthe control unit of the PCEF device may further be arranged fortriggering a de-installation of said initial control rules.

Also in this respect, and in accordance with another embodiment of theinvention, the receiver of the PCEF device may further be arranged forreceiving the initial control rules from the PCRF server along with anindication of being temporary control rules valid only during aconfigurable time period. In this embodiment, the control unit of thePCEF device may further be arranged for triggering a de-installation ofsaid initial control rules upon expiry of said time period. Moreover,also in this embodiment and aligned with a corresponding feature of thePCRF server, the sender of the PCEF device may further be arranged forsubmitting an indication towards the PCRF server informing that theinitial control rules have been de-installed after expiry of said timeperiod.

Aligned with corresponding embodiments for the PCRF server, where thefinal control rules include new control rules complementing the initialcontrol rules, the receiver of the PCEF device may further be arrangedfor receiving an indication of such complement, and the control unit ofthe PCEF device may further be arranged for adding the new control rulesto the initial control rules previously installed and for consideringthe addition as the final control rules. However, where the finalcontrol rules are new control rules, the control unit of the PCEF devicemay further be arranged for triggering the de-installation of theinitial control rules in response to the receiver of the PCEF devicereceiving said final control rules.

Also aligned with an advantageous embodiment explained above, thereceiver of the PCEF device may further be arranged for receiving anindication, along with the initial control rules, indicatinginstallation with a “gate status” set to disabled.

The invention may be practised by one or more computer programs,loadable into an internal memory of a number of computers, each one withinput and output units as well as with a processing unit, the computerprogram comprising executable code adapted to carry out method stepsaccording to the above method when running in the computer. Theexecutable code of the one or more computer programs may be recorded ina carrier readable in a computer.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects and advantages of the invention will becomeapparent by reading this description in conjunction with theaccompanying drawings, in which:

FIG. 1 represents a PCC architecture of an exemplary scenario where afirst user connected through a GPRS network as IP-CAN holds an IMSsession with a second user connected through evolved packet system(hereinafter EPS) as IP-CAN.

FIGS. 2 a and 2 d illustrate a sequence of actions to be followed inaccordance with the invention at the originating side of an IMS sessionto be established in an exemplary scenario for Multimedia Telephony.

FIGS. 2 b and 2 c illustrate a sequence of actions to be followed inaccordance with the invention at the destination side of an IMS sessionto be established in an exemplary scenario for Multimedia Telephony.

FIG. 2 e 1 illustrates an exemplary termination of a pre-authorizationat the originating side of an IMS session where the timing is carriedout in the PCRF sever.

FIG. 2 e 2 illustrates an exemplary termination of a pre-authorizationat the originating side of an IMS session where the timing is carriedout in the PCEF device.

FIG. 2 f 1 illustrates an exemplary termination of a pre-authorizationat the destination side of an IMS session where the timing is carriedout in the PCRF sever.

FIG. 2 f 2 illustrates an exemplary termination of a pre-authorizationat the destination side of an IMS session where the timing is carriedout in the PCEF device.

FIG. 3 illustrates structural elements included in a PCRF server, aswell as connections towards other architectural nodes.

FIG. 4 illustrates structural elements included in a PCEF device, aswell as connections towards other architectural nodes.

FIG. 5 illustrates an exemplary embodiment of the sequence of actionsthat may be carried out to obtain at a PCRF server an indication ofallowance of pre-authorization from a P-CSCF where media components arenegotiated through.

DETAILED DESCRIPTION

The following describes some preferred embodiments for supporting thereservation of bearer resources before having received a correspondingQoS Authorization for such reservation.

FIG. 2 a-2 d illustrate the most significant actions to be followed atthe originating side where a first UE 4 a, namely UE-1, invites a secondUE 4 b, namely UE-2, at a destination side to establish a mediacommunication through the IMS. As illustrated in FIG. 1, said UE-1 4 aestablishes an IP-CAN session through an exemplary GPRS access networkso that the media can be submitted towards the destination network via aServing GPRS Support Node (hereinafter SGSN) 8 a and a GGSN 7 a. In thisrespect, a first PCEF device 2 a, namely PCEF-1, is included in the GGSN7 a and is in charge of handling bearer resources for transport of suchmedia and of enforcing control rules for the corresponding IP-flowsthrough the bearer. On the other hand, the signalling required tonegotiate the media transmission is exchanged between the UE-1 4 a andthe UE-2 4 b through the IMS network. In particular and referring to theillustration in FIG. 1, the UE-1 4 a in the originating networkexchanges signalling related to the IMS session with a first P-CSCF 5 a,namely P-CSCF-1, in the originating side of its IMS network, whereas theUE-2 4 b in the destination network exchanges signalling related to theIMS session with a second P-CSCF 5 b, namely P-CSCF-2, in thedestination side of its IMS network. Between the P-CSCF-1 5 a and theP-CSCF-2 5 b there may be number of intermediate IMS nodes, notsignificant for the purpose of the present invention, and represented bya so-called IMS Core 6 throughout this specification. In this exemplaryscenario shown in FIG. 1, the UE-2 4 b establishes an IP-CAN sessionthrough an exemplary evolved packet system (hereinafter EPS) so that themedia can be submitted towards the originating network via a ServingGateway (hereinafter SGW) 8 b and a Packet Data Network Gateway(hereinafter PDN-GW) 7 b. In this respect, a second PCEF device 2 b,namely PCEF-2, is included in the PDN-GW 7 b and is in charge, as forthe originating side, of handling bearer resources for transport of suchmedia and of enforcing control rules for the corresponding IP-flowsthrough the bearer resource. The GGSN 7 a and the PDN-GW 7 b indeedtransfer media to each other through other network nodes not shown forthe sake of clarity. Moreover, both P-CSCF-1 and P-CSCF-2 respectivelylocated at originating and destination sides, respectively communicatewith a first PCRF server 1 a, namely PCRF-1, and a second PCRF server 1b, namely PCRF-2, both PCRF-1 and PCRF-2 installing appropriate controlrules to respective PCEF-1 and PCEF-2. Furthermore, P-CSCF-1, P-CSCF-2,or both may include a respective AF, namely AF-1 and AF-2, in accordancewith the PCC architecture described above.

The sequence of actions illustrated in FIG. 2 a starts with a step S-010of submitting an invitation to negotiate a media communication, whichincludes a so-called SDP offer with significant descriptions of mediacomponents, from an originating UE-1 4 a towards a second UE at adestination side through the IMS. This invitation to negotiate the mediacommunication is received at the P-CSCF-1 5 a in the originating side ofthe IMS, and forwarded towards the IMS Core 6 during a step S-015.

The sequence of actions occurring at the destination side continue asillustrated in FIG. 2 b. However, in a scenario where the above problemaiming the present invention turns up, the reservation of bearerresources may be initiated by the originating UE-1 4 a immediately afterhaving submitted the initial invitation request. Accordingly, and backto sequence of actions illustrated in FIG. 2 a, the originating UE-1 4 asubmits a request for bearer resources during a step S-020 towards thePCEF-1 2 a likely located in the exemplary GGSN 7 a of the IP-CAN in theoriginating side. Responsive to receipt of such request for bearerresources, the PCEF-1 2 a submits a request for control rules during astep S-025 towards the PCRF-1 1 a at the originating side. Upon receiptof such request for control rules in the PCRF-1 1 a, the PCRF-1determines during a step S-030 that a QoS authorization has not beenreceived yet for such bearer request and initial control rules to beinstalled. Thereafter, the PCRF-1 1 a initiates a pre-authorizationprocedure during a step S-035, procedure which in an embodiment of theinvention may trigger a timing of a configured time period during whichthe initial control rules and the pre-authorization are valid, and inanother embodiment includes a step of indicating towards the PCEF-1,along with the initial control rules, that the initial control rules aretemporary control rules valid only during a configurable time period. Asa result, the PCRF-1 1 a installs towards the PCEF-1 2 a said initialcontrol rules during a step S-040 and marks the Qos authorization ispending, and the PCEF-1, once said initial control rules are installed,submits during a step S-045 a successful response towards theoriginating UE-1 4 a.

Advantageously, the installation of initial control rules includes anindication submitted towards the PCEF device 2 a, 2 b indicating theinstallation with a “gate status” set to disabled, so that the bearerresources are reserved but traffic is still prevented on such bearerresources.

As already commented above, these initial control rules may includeinformation elements selected from: a rule identifier; a gate status; anincomplete service data flow template, as obtainable from informationprovided by the user equipment; QoS information including a QoS classidentifier “QCI”, a guaranteed bit rate “GBR” and a maximum bit rate“MBR”, as requested by the IP-CAN; and optional configured data such ascharging information, service identifier, precedence, etc.

At this stage, nothing significant occurs at the originating side untilreceiving either an SDP answer from the destination side or, under theabove embodiment of timing the time period in the PCRF-1, a timeout ofsaid time period, what is further described.

Before describing the next sequence of actions to occur at theoriginating side, and given that a possible termination requires thereception of an SDP answer from the destination side, the followingdescribes the sequence of actions occurring upon receipt of theoriginating SDP answer at the destination side, as illustrated in FIG. 2b.

Thus, the sequence of actions occurring at the destination side, as FIG.2 b illustrates, starts when the IMS Core 6 submits towards thedestination P-CSCF-2 5 b the originating SDP offer during a step S-050.Then, the P-CSCF-2 5 b forwards such SDP offer during a step S-055towards the destination UE-2 4 b, and said destination UE-2 may thussubmit a request for bearer resources during a step S-060 towards thePCEF-2 2 b. This PCEF-2 may be located in an exemplary GGSN of theIP-CAN not illustrated in any drawing, as in the originating side, ormay likely be located in a PDN-GW 7 b as FIG. 1 exemplary illustrates.Responsive to the receipt of such request for bearer resources, thePCEF-2 2 b submits a request for control rules during a step S-065towards the PCRF-2 1 b at the destination side. Upon receipt of suchrequest for control rules in the PCRF-2 1 b, the PCRF-2 determinesduring a step S-070, as explained above for the originating side, that aQoS authorization has not been received yet for such bearer request andinitial control rules to be installed. As at the originating side, thePCRF-2 1 b initiates a pre-authorization procedure during a step S-075and marks the Qos authorization is pending, procedure which in anembodiment of the invention may trigger a timing of a configured timeperiod during which the initial control rules and the pre-authorizationare valid, and in another embodiment includes a step of indicatingtowards the PCEF-2, along with the initial control rules, that theinitial control rules are temporary control rules valid only during aconfigurable time period. As a result, the PCRF-2 1 b installs towardsthe PCEF-2 2 b said initial control rules during a step S-080, and thePCEF-2, after having installed said initial control rules, submitsduring a step S-085 a successful response towards the destination UE-2 4b.

Advantageously, the installation of initial control rules includes anindication submitted from the PCRF server 1 a, 1 b towards the PCEFdevice 2 a, 2 b indicating the installation with a “gate status” set todisabled, so that the bearer resources are reserved but traffic is stillprevented on such bearer resources.

Initial rules that, as for the originating side, may include informationelements selected from: a rule identifier; a gate status; an incompleteservice data flow template, as obtainable from information provided bythe user equipment; QoS information including a QoS class identifier“QCI”, a guaranteed bit rate “GBR” and a maximum bit rate “MBR”, asrequested by the IP-CAN; and optional configured data such as charginginformation, service identifier, precedence, etc.

A conventional PCRF server may comprise a receiver 12 for receiving aQoS authorization of a bearer resource and for receiving a correspondingrequest for the bearer resource; a control unit 10 for determining a setof control rules to be installed for handling the requested bearerresource once authorized; and a sender 11 for installing said set ofcontrol rules towards the PCEF device 2 a, 2 b. However, a PCRF server 1a, 1 b may be adapted in accordance with the invention as illustrated inFIG. 3, so that the control unit 10 is arranged for pre-authorizing therequest of a bearer resource, the request received before havingreceived the QoS authorization; and the sender 11 is arranged forinstalling the initial control rules applicable to the pre-authorizedrequest.

A conventional PCEF device for enforcing control rules on a per bearerresource basis, may comprise a sender 21 for submitting a request for abearer resource, a receiver 22 for receiving control rules to beinstalled for the bearer resource, and a control unit 20 for applyingthe control rules to the bearer resource. However, a PCEF device 2 a, 2b may be adapted in accordance with the invention as illustrated in FIG.4, so that the receiver 22 is arranged for receiving the initial controlrules applicable to said bearer resource pre-authorized by the PCRFserver 1 a, 1 b before having a QoS authorization available.

Moreover, the sender 11 of the PCRF device 1 a, 1 b may further bearranged for submitting an indication towards the PCEF device 2 a, 2 b,along with the initial control rules, indicating that the initialcontrol rules are temporary control rules valid only during aconfigurable time period to be controlled at the PCEF device 2 a, 2 b;and the receiver 22 of the PCEF device 2 a, 2 b may further be arrangedfor receiving such indication, along with the initial control rules, andthe control unit 20 of the PCEF device 2 a, 2 b may further be arrangedfor timing such configurable time period.

Furthermore, the sender 11 of the PCRF device 1 a, 1 b may further bearranged for submitting an indication towards the PCEF device 2 a, 2 b,along with the initial control rules, indicating installation with a“gate status” set to disabled; and the receiver 22 of the PCEF device 2a, 2 b may further be arranged for receiving an indication, along withthe initial control rules, indicating installation with a “gate status”set to disabled.

The sequence of actions continues at the destination side as illustratedin FIG. 2 c wherein the destination UE-2 4 b, after having successfullyreserved bearer resources, can return towards the originating side acorresponding SDP answer during a step S-090.

This SDP answer is received in the P-CSCF-2 5 b of the destination sidewhich, prior to forwarding such SDP answer towards the originating side,submits the QoS authorization towards the PCRF-2 1 b.

Upon receipt of the QoS authorization, and based on media componentdescriptions included therein, the PCRF-2 1 b determines during a stepS-100 final control rules to be installed towards the PCEF-2, and stopsthe ongoing pre-authorization procedure for any embodiment of thoseexplained above in this respect and resets the mark of Qos authorizationbeing pending. In particular, where the time period is running at thePCRF-2 1 b, a corresponding timer is stopped therein.

Then, the PCRF-2 1 b submits during a step S-110 the final control rulesto be installed at the PCEF-2 2 b. These final control rules may includenew control rules complementing the initial control rules, in which casethe PCRF-2 1 b may indicate such complement towards the PCEF-2 2 b, orthe final control rules may be new control rules, in which case thePCRF-2 1 b may also indicate such event towards the PCEF-2 2 b. Inparticular, where the final control rules are new control rules, itssubmission may be considered an implicit de-installation of initialcontrol rules.

These final control rules may thus be completed or amended in accordancewith service information received along with the Qos authorization and,in particular, in accordance with the media component descriptionsincluded therein. That is, these final control rules may includeinformation elements selected from: the rule identifier; the gatestatus; the complete service data flow template; the complete QoSinformation; and charging information, service identifier, precedence,etc, as received along with the QoS authorization.

To this end, the PCRF server 1 a, 1 b, as illustrated in FIG. 3 may beadapted in accordance with the invention so that the sender 11 isarranged for further updating the previously installed initial controlrules with final control rules upon receipt of the QoS authorization.Moreover, the sender 11 may be arranged for indicating towards the PCEFdevice 2 a, 2 b whether the final control rules complement the initialcontrol rules, or are new control rules to replace the initial controlrules. Aligned with this embodiment, the receiver 22 of the PCEF device2 a, 2 b may be arranged for receiving an indication that the newcontrol rules complement the initial control rules, and the control unit20 may further be arranged for adding the new control rules to theinitial control rules previously installed and for considering theaddition as the final control rules; and, where the final control rulesare new control rules, the control unit 20 may further be arranged fortriggering a de-installation of the initial control rules responsive tothe receiver 22 receiving said final control rules.

Still with reference to FIG. 2 c, the PCEF-2 2 b, upon receipt of thefinal control rules, initiates a procedure of updating the initial withthese final control rules during a step S-115. In this respect, wherethere is an indication of being a complement to the initial controlrules, this procedure may be adapted for adding said new control rulesto the initial control rules previously installed in order to configurethe final control rules, without needing removal and re-installation ofunchanged initial control rules. On the other hand, where there is anindication of being considered new control rules, the procedure isadapted for implicitly de-installing the initial control rules and theninstalling the final control rules.

After having successfully installed the final control rules, the PCEF-2confirms such updating towards the PCRF-2 1 b during a step S-120, andthe PCRF-2 confirms the QoS authorization towards the P-CSCF-2 5 bduring a step S-125. Then, the P-CSCF-2 can eventually forward the SDPanswer towards the originating side via the IMS Core 6 during a stepS-130.

The sequence of actions now continues at the originating side asillustrated in FIG. 2 d wherein the IMS Core 6 forwards the SDP answertowards the P-CSCF-1 5 a in the originating side during a step S-140.This P-CSCF-1 5 a at the originating side, prior to forwarding such SDPanswer towards the UE-1 4 a, submits the QoS authorization towards thePCRF-1 1 a.

In a similar manner as at the destination side, upon receipt of the QoSauthorization and based on media component descriptions includedtherein, the PCRF-1 1 a determines during a step S-150 final controlrules to be installed towards the PCEF-1 2 a, resets the mark of QoSauthorization being pending, and stops the ongoing pre-authorizationprocedure for the applicable embodiment of those explained above in thisrespect. That is, where the time period is running at the PCRF-1 1 a, acorresponding timer is stopped therein; otherwise, other correspondingindicators may be reset.

Then, the PCRF-1 1 a submits during a step S-160 the final control rulesto be installed at the PCEF-1 2 a. These final control rules may includenew control rules complementing the initial control rules, in which casethe PCRF-1 1 a may indicate such complement towards the PCEF-1 2 a, orthe final control rules may be new control rules, in which case thePCRF-1 1 a may also indicate such event towards the PCEF-1 2 a.

Also in a similar manner as done at the destination side upon receipt ofthe final control rules, the PCEF-1 2 a initiates a procedure ofupdating the initial with these final control rules during a step S-165.In this respect, where there is an indication of being a complement tothe initial control rules, this procedure may be adapted for adding saidnew control rules to the initial control rules previously installed inorder to configure the final control rules, without needing removal andre-installation of unchanged initial control rules. On the other hand,where there is an indication of being considered new control rules, theprocedure is adapted for implicitly de-installing the initial controlrules and then installing the final control rules.

Moreover, the PCEF device 2 a, 2 b may be adapted in accordance with theinvention as illustrated in FIG. 4, so that the receiver 22 is arrangedfor receiving final control rules from the PCRF server 1 a, 1 b toupdate said initial control rules once the QoS authorization isavailable, and the control unit 20 is arranged for updating said initialcontrol rules with the final control rules upon receipt of such updatingfrom the PCRF server 1 a, 1 b.

Still with reference to FIG. 2 d, once the final control rules havesuccessfully been installed, the PCEF-1 2 a confirms such updatingtowards the PCRF-1 1 a during a step S-170, and the PCRF-1 confirms theQoS authorization towards the P-CSCF-1 5 a during a step S-175.Afterwards, the P-CSCF-1 can eventually forward the SDP answer towardsthe UE-1 4 a during a step S-180.

The description of the sequence of actions hereinbefore, namely thosewith reference to the illustrations in FIG. 2 a-2 d, correspond to thepre-authorization proceedings that can be followed at any of theoriginating side, the destination side, or both, where suchpre-authorization is followed by a QoS authorization expected undercurrently existing procedures to establish an IMS session between anoriginating and a destination end.

In this respect, the network may be organized in such a manner that onlythe originating side, only the destination side, or both sides areadapted for allowing pre-authorization of a bearer reservation beforehaving received a corresponding QoS authorization with the descriptionsof the media components for the IMS session.

The present invention thus provides for a solution to avoid rejection ofa request to install control rules received before having received acorresponding QoS Authorization, even in a scenario where the QoSAuthorization is conditioned to a prior reservation of resources.

Nevertheless, this pre-authorization cannot be regarded as a finalauthorization replacing the QoS authorization with the descriptions ofthe media components for the IMS session. Therefore, the presentinvention provides for a configurable time period during which thepre-authorization and the initial control rules are valid whilstawaiting the receipt of said QoS authorization. The timing of thisconfigurable time period may be carried out either at the PCRF server 1a, 1 b, or at the PCEF device 2 a, 2 b of the originating or destinationside of the IMS session in accordance with different embodiments of thepresent invention and, in particular, nothing in this teaching preventsfrom timing at the PCRF server 1 a at the originating side and timing atthe PCEF device 2 b at the destination side, or vice versa. Thesedifferent combinations are described in the following with reference tothe sequence of actions shown in FIGS. 2 e 1, 2 e 2, 2 f 1 and 2 f 2.

Thus, after having installed the initial control rules at the PCEF-1 2 aduring the step S-040 and having submitted a successful response to therequest of bearer resources towards the originating UE-1 4 a during thestep S-045, as illustrated in FIG. 2 a, a first embodiment of timing atthe originating side is illustrated in FIG. 2 e 1 wherein the PCRF-1 1 acontrols the configurable time period. Under this embodiment, the QoSauthorization expected to be received during the step S-145, asexplained above in respect of FIG. 2 d, is not received upon expirationduring a step S-200 of the configurable time period. Where said timeperiod has expired at the PCRF-1 1 a during the step S-200, thepre-authorization procedure is stopped during a step S-205, thecorresponding bearer resource is de-authorized, the mark of QoSauthorization pending is reset and an instruction to de-install theinitial control rules is submitted towards the PCEF-1 2 a during a stepS-210. The PCEF-1 2 a receiving such instruction removes the initialcontrol rules during a step S-215 and may submit an indication towardsthe originating UE-1 indicating the release of corresponding bearerresources.

To this end, and given that the initial control rules are temporarycontrol rules valid only during a configurable time period withouthaving received the QoS authorization, the sender 11 of the PCRF server1 a, 1 b, as illustrated in FIG. 3, may be arranged for de-installingtowards the PCEF device 2 a, 2 b the initial control rules after expiryof said time period. Aligned with this embodiment, the receiver 22 ofthe PCEF device 2 a, 2 b, as illustrated in FIG. 4, may further bearranged for receiving a de-installation of said initial control rulesfrom the PCRF server 1 a, 1 b, and the control unit 20 of the PCEFdevice may further be arranged for triggering a de-installation of saidinitial control rules.

Still in the situation where the initial control rules had beeninstalled at the PCEF-1 2 a during the step S-040 and the successfulresponse to the request of bearer resources had been submitted towardsthe originating UE-1 4 a during the step S-045, as illustrated in FIG. 2a, a second embodiment of timing at the originating side is illustratedin FIG. 2 e 2 wherein the PCEF-1 2 a controls the configurable timeperiod. Under this second embodiment illustrated in FIG. 2 e 2, theinstruction to install final control rules expected to be receivedduring the step S-160, as explained above in respect of FIG. 2 d, is notreceived upon expiration during a step S-230 of the configurable timeperiod. Where said time period has expired at the PCEF-1 2 a during thestep S-230, the initial control rules are removed at the PCEF-1 2 aduring a step S-235 and an indication is submitted during a step S-240towards the PCRF-1 1 a indicating that the initial control rules havebeen de-installed and, implicitly, the expiration of thepre-authorization. The PCRF-1 1 a, upon receipt of such indication,terminates the pre-authorization procedure during a step S-245. As forthe first procedure, the PCEF-1 may submit an indication towards theoriginating UE-1 indicating the release of corresponding bearerresources.

To this end, and given that the initial control rules are temporarycontrol rules valid only during a configurable time period withouthaving received the QoS authorization, the control unit 20 of the PCEFdevice 2 a, 2 b, as illustrated in FIG. 4, may further be arranged fortriggering a de-installation of said initial control rules upon expiryof said time period, and the sender 21 of the PCEF device 2 a, 2 b maybe arranged for submitting an indication towards the PCRF server 1 a, 1b informing that the initial control rules have been de-installed afterexpiry of said time period; whereas the receiver 12 of the PCRF server 1a, 1 b, as illustrated in FIG. 3, may be arranged for receiving anindication from the PCEF device 2 a, 2 b informing that the initialcontrol rules have been de-installed after expiry of said time.

On the other hand, similar embodiments may be applied at the destinationside. Thus, after having installed the initial control rules at thePCEF-2 2 b during the step S-080 and having submitted a successfulresponse to the request of bearer resources towards the destination UE-24 b during the step S-085, as illustrated in FIG. 2 b, a firstembodiment of timing at the destination side is illustrated in FIG. 2 f1 wherein the PCRF-2 1 b controls the configurable time period. Underthis embodiment, the QoS authorization expected to be received duringthe step S-095, as explained above in respect of FIG. 2 c, is notreceived upon expiration during a step S-250 of the configurable timeperiod. Where said time period has expired at the PCRF-2 1 b during thestep S-250, the pre-authorization procedure is stopped during a stepS-255, and an instruction to de-install the initial control rules issubmitted towards the PCEF-2 2 b during a step S-260. The PCEF-2 2 breceiving such instruction removes the initial control rules during astep S-265 and may submit an indication towards the destination UE-2indicating the release of corresponding bearer resources. In thisembodiment, as well as in the corresponding one at the originating side,the PCRF-2 1 b may also remove the initial control rules during a stepS-270, if stored on the basis of this pre-authorization.

To this end, depending on the implementation, the control unit 10 of thePCRF server 1 a, 1 b, in the originating side as well as in thedestination side, may also be arranged for removing said initial controlrules.

Still in the situation where the initial control rules had beeninstalled at the PCEF-2 2 b during the step S-080 and the successfulresponse to the request of bearer resources had been submitted towardsthe destination UE-2 4 b during the step S-085, as illustrated in FIG. 2b, a second embodiment of timing at the destination side is illustratedin FIG. 2 f 2 wherein the PCEF-2 2 b controls the configurable timeperiod. Under this second embodiment illustrated in FIG. 2 f 2, theinstruction to install final control rules expected to be receivedduring the step S-110, as explained above in respect of FIG. 2 c, is notreceived upon expiration during a step S-280 of the configurable timeperiod. Where said time period has expired at the PCEF-2 2 b during thestep S-280, the initial control rules are removed at the PCEF-2 2 bduring a step S-285 and an indication is submitted during a step S-290towards the PCRF-2 1 b indicating that the initial control rules havebeen de-installed and, implicitly, the expiration of thepre-authorization. The PCRF-2 1 b, upon receipt of such indication,terminates the pre-authorization procedure during a step S-295 and mayalso remove the initial control rules during a step S-300, if stored onthe basis of this pre-authorization. As for the first procedure, thePCEF-2 may also submit an indication towards the destination UE-2indicating the release of corresponding bearer resources.

Regarding the capability of pre-authorizing a request for a bearerresource, the present invention provides for two main embodiments. In afirst embodiment, the PCRF server 1 a, 1 b is configured to decide andallow such pre-authorization on its own; whereas in a second embodiment,the PCRF server 1 a, 1 b in the originating or destination side obtainssuch permit from a P-CSCF 5 a, 5 b in said originating or destinationside. In this respect, the sequence of actions illustrated in FIG. 2 a-2d, 2 e 1, 2 e 2, 2 f 1 and 2 f 2 may assume any of these twoembodiments, namely the PCRF server 1 a, 1 b being configured to decideand allow such pre-authorization on its own or the PCRF server 1 a, 1 bobtaining such permit from the P-CSCF 5 a, 5 b. Notwithstanding this,the sequence of actions illustrated in FIG. 2 a-2 d, 2 e 1, 2 e 2, 2 f 1and 2 f 2 may also assume only the second embodiment as described in thefollowing.

Thus, FIG. 5 illustrates an exemplary embodiment where the P-CSCF-2 5 bin the destination side, upon receiving the SDP offer during the stepS-050 and before forwarding it to the destination UE-2 4 b during thestep S-055 as described above in respect of FIG. 2 b, submits during astep S-310 an indication towards the PCRF-2 1 b at the destination sideindicating that the pre-authorization is allowed. The PCRF-2 1 breceiving such indication marks during a step S-315 a pre-authorizationpending for a further request for a bearer resource from the destinationUE-2 4 b, and returns towards the P-CSCF-2 5 b during a step S-320 aconfirmation of having enabled the further pre-authorization. Once suchconfirmation is received, the P-CSCF-2 5 b may continue with theforwarding the SDP offer towards the destination UE-2 4 b during thestep S-055 and the next sequence of actions as illustrated in FIG. 2 b,namely the request for bearer resources during the step S-060 towardsthe PCEF-2 2 b and, responsive to the receipt of such request for bearerresources, the PCEF-2 2 b submitting the request for control rulesduring the step S-065 towards the PCRF-2 1 b at the destination side.

This particular embodiment exemplary illustrated with reference to FIG.5 in the destination side may also effectively be carried out bycorresponding entities in the originating side, namely the P-CSCF-1 5 aand the PCRF-1 1 a.

To this end, the receiver 12 of the PCRF server 1 a, 1 b may be arrangedfor receiving a pre-authorization indication from the P-CSCF server 5 a,5 b and the control unit 10 of the PCRF server 1 a, 1 b may be arrangedfor carrying out this pre-authorization in response to saidpre-authorization indication.

Moreover, and in accordance with a further aspect of the invention,there is also provided a P-CSCF server 5 a, 5 b, in the originating sideor destination side of the IMS session, where a given user 4 a, 4 baccesses the IMS through for communicating with another end user 4 b, 4a. This P-CSCF conventionally comprises a sender for submitting a QoSauthorization towards the PCRF server 1 a, 1 b, which is in charge ofproviding control functions and installing control rules. In accordancewith this further aspect of the invention, the P-CSCF server may beadapted so that the sender is arranged for submitting during a stepS-310 a pre-authorization of a request of a bearer resource beforehaving received significant descriptions of media components negotiatedbetween the given user and the another end user.

In particular, and depending on the IP-CAN where the originating ordestination user accesses the IMS through, the PCEF device 2 a, 2 b maybe included in a GGSN 7 a or in a PDN-GW 7 b.

Regarding implementation of embodiments, the invention can be realizedby a computer program, which is loadable into an internal memory of acomputer that includes input and output units as well as a processingunit. This computer program comprises executable code portions adaptedto carry out sequences of actions described under the above embodimentswhen running in the computer. In particular, the computer program may berecorded in a carrier computer-readable medium, such as a CD-ROM.

The invention is described above in respect of several embodiments in anillustrative and non-restrictive manner. Obviously, variations, andcombinations of these embodiments are possible in light of the aboveteachings, and any modification of the embodiments that fall within thescope of the claims is intended to be included therein.

1. A method of authorizing a request for a bearer resource receivedbefore having received a Quality of Service (QoS) authorization for saidrequest, the method comprising the steps of: receiving a request for abearer resource; and determining that a QoS authorization has not beenreceived for said request at a Policy and Charging Rules Function (PCRF)server; pre-authorizing said request for the bearer resource receivedbefore having received the QoS authorization; installing initial controlrules applicable to the pre-authorized request towards a Policy andCharging Enforcement Function (PCEF) device; and updating the previouslyinstalled initial control rules with final control rules upon receipt ofthe QoS authorization.
 2. The method of claim 1, wherein the initialcontrol rules are temporary control rules valid only during aconfigurable time period without having received the QoS authorizationat the PCRF server.
 3. The method of claim 2, wherein thepre-authorization is valid only during a configurable time period, andfurther comprising a step of de-authorizing the bearer resource uponexpiry of said time period without having received the QoSauthorization.
 4. The method of claim 3, further comprising a step ofde-installing towards the PCEF device the initial control rules afterexpiry of said time period without having received the QoSauthorization.
 5. The method of claim 1, wherein the step of installingthe initial control rules towards the PCEF device includes a step ofindicating that temporary control rules are valid only during aconfigurable time period.
 6. The method of claim 5, further comprising astep of receiving at the PCRF server anindication from the PCEF deviceinforming that the initial control rules have been de-installed afterexpiry of said time period, and a step of removing said initial controlrules.
 7. The method of claim 1, wherein the final control rules includenew control rules complementing the initial control rules, and themethod further includes a step of indicating such complement from thePCRF server towards the PCEF device.
 8. The method of claim 7, furthercomprising a step of adding said new control rules to the initialcontrol rules previously installed at the PCEF device to configure thefinal control rules.
 9. The method of claim 1, wherein the final controlrules are new control rules, and the method further comprising a step ofimplicitly de-installing the initial control rules and a step ofinstalling the final control rules towards the PCEF device.
 10. Themethod of claim 1, wherein the step of installing initial control rulesincludes a step of indicating installation with a gate status set todisabled.
 11. The method of claim 1, further including a step of timinga configurable time period during which the pre-authorization and theinitial control rules are valid and after which, without having receivedthe QoS authorization, the corresponding bearer resource isde-authorized and the initial control rules are de-installed.
 12. Themethod of claim 11, wherein the step of timing the configurable timeperiod is carried out by at least one of the PCRF server and the PCEFdevice.
 13. The method of claim 1, further including a step of obtaininga pre-authorization indication at the PCRF server from a Proxy CallSession Control Function (P-CSCF) server.
 14. A Policy and ChargingRules Function (PCRF) server comprising: a receiver for receiving aQuality of Service (QoS) authorization of a bearer resource and forfurther receiving a corresponding request for the bearer resource; acontrol unit for determining a set of control rules to be installed forhandling the requested bearer resource once authorized; a sender forinstalling said set of control rules towards a Policy and ChargingEnforcement Function (PCEF) device; the control unit being arranged forpre-authorizing a request of a bearer resource, the request receivedbefore having received the QoS authorization; and the sender beingarranged for installing initial control rules applicable to thepre-authorized request and for further updating the previously installedinitial control rules with final control rules upon receipt of the QoSauthorization.
 15. The PCRF server of claim 14, wherein the initialcontrol rules are temporary control rules valid only during aconfigurable time period without having received the QoS authorization.16. The PCRF server of claim 15, wherein the sender is arranged forde-installing towards the PCEF device the initial control rules afterexpiry of said time period.
 17. The PCRF server of claim 14, wherein thepre-authorization is valid only during a configurable time period uponwhich expiry, without having received the QoS authorization, thecorresponding bearer resource is de-authorized at the control unit. 18.The PCRF server of claim 14, wherein the sender is arranged forinstalling the initial control rules along with an indication of beingtemporary control rules valid only during a configurable time period.19. The PCRF server of claim 18, wherein the receiver is arranged forreceiving an indication from the PCEF device informing that the initialcontrol rules have been de-installed after expiry of said time period,and the control unit is arranged for removing said initial controlrules.
 20. The PCRF server of claim 14, wherein the final control rulesinclude new control rules complementing the initial control rules, andthe sender is arranged for indicating such complement towards the PCEFdevice.
 21. The PCRF server of claim 14, wherein the final control rulesare considered new control rules implicitly de-installing the initialcontrol rules towards the PCEF device.
 22. The PCRF server of claim 14,wherein the initial control rules are installed with a gate status setto disabled.
 23. The PCRF server of claim 14, wherein thepre-authorization may be carried out by the control unit upon receipt inthe receiver of a pre-authorization indication from a Proxy Call SessionControl Function (P-CSCF) server.
 24. The PCRF server of claim 14,wherein the QoS authorization for reserving a bearer is received from aProxy Call Session Control Function server.
 25. A Policy and ChargingEnforcement Function (PCEF) device for enforcing control rules on a perbearer resource basis, having a sender for submitting a request for abearer resource, a receiver for receiving control rules to be installedfor the bearer resource, and a control unit for applying the controlrules to the bearer resource, the receiver being arranged for receivinginitial control rules applicable to said bearer resource pre-authorizedby a Policy and Charging Rules Function (PCRF) server before having aQuality of Service (QoS) authorization available, and for receivingfinal control rules from the PCRF server to update said initial controlrules once the QoS authorization is available and the control unit isarranged for updating said initial control rules with final controlrules upon receipt of such updating from the PCRF server.
 26. The PCEFdevice of claim 25, wherein the initial control rules are temporarycontrol rules valid only during a configurable time period withouthaving received the final control rules from the PCRF server.
 27. ThePCEF device of claim 26, wherein the receiver is further arranged forreceiving a de-installation of said initial control rules from the PCRFserver and the control unit is further arranged for triggering ade-installation of said initial control rules.
 28. The PCEF device ofclaim 25, wherein the receiver is further arranged for receiving theinitial control rules along with an indication of being temporarycontrol rules valid only during a configurable time period.
 29. The PCEFdevice of claim 28, wherein the control unit is further arranged fortriggering a de-installation of said initial control rules upon expiryof said time period.
 30. The PCEF device of claim 29, wherein the senderis arranged for submitting an indication towards the PCRF serverinforming that the initial control rules have been de-installed afterexpiry of said time period.
 31. The PCEF device of claim 25, wherein thefinal control rules include new control rules complementing the initialcontrol rules, the receiver is arranged for receiving an indication ofsuch complement, and the control unit is further arranged for adding thenew control rules to the initial control rules previously installed andfor considering the addition as the final control rules.
 32. The PCEFdevice of claim 25, wherein the final control rules are new controlrules, and the control unit is further arranged for triggeringde-installation of the initial control rules in response to the receiverreceiving said final control rules.
 33. The PCEF device of claim 25,wherein the receiver is further arranged for receiving an indication,along with the initial control rules, indicating installation with a setto disabled.
 34. The PCEF device of claim 25, comprising a Gateway GPRSSupport Node (GGSN).
 35. The PCEF device of claim 25, comprising aPacket Data Network Gateway (PDN-GW).
 36. A Proxy Call Session ControlFunction (P-CSCF) server where a given user accesses an IP MultimediaSubsystem (IMS) through for communicating with another end user, theP-CSCF comprising a sender for submitting a Quality of Service (QoS)authorization towards a Policy and Charging Rules Function (PCRF) serverin charge of providing control functions and installing control rules,the sender being arranged for submitting a pre-authorization of arequest of a bearer resource before having received significantdescriptions of media components negotiated between the given user andthe another end user.
 37. (canceled)
 38. (canceled)